1. Field of the Invention
The present invention relates to a cooling cycle apparatus and a method of controlling a linear expansion valve of the same, and, more particularly, to a cooling cycle apparatus and a method of controlling a linear expansion valve of the same that is capable of controlling the linear expansion valve based on suction overheat level of compressors, whereby the cooling cycle apparatus quickly deals with load, and therefore, reliability of the cooling cycle apparatus is improved.
2. Description of the Related Art
Generally, a cooling cycle apparatus is an apparatus that cools or heats the interior of a room where a specific component of the cooling cycle apparatus is installed. The cooling cycle apparatus comprises a compressor, a condenser, an expansion mechanism, and a vaporizer.
In recent years, a plurality of compressors have been mounted in cooling cycle apparatuses, or a liner compressor whose compression capacity is variable has been mounted in cooling cycle apparatuses, in order to properly operate the cooling cycle apparatuses based on cooling load or heating load. Also, a linear expansion valve has been used to control the expansion level of the expansion mechanism when the compression capacity of the compressor is to be controlled.
For convenience, a description of a heat pump type cooling cycle apparatus, which is operated not only in cooling operation mode but also in heating operation mode, will be given hereinafter.
FIG. 1 is a circuit diagram showing the flow of refrigerant when a conventional cooling cycle apparatus is operated in cooling operation mode, and FIG. 2 is a circuit diagram showing the flow of refrigerant when the conventional cooling cycle apparatus is operated in heating operation mode.
As shown in FIGS. 1 and 2, the conventional cooling cycle apparatus comprises: a pair of compressors 1a and 1b for compressing low-temperature and low-pressure gas refrigerant into high-temperature and high-pressure gas refrigerant; an outdoor heat exchanger 4 for performing heat exchange between the refrigerant and outdoor air to condense/vaporize the refrigerant; an indoor heat exchanger 6 for performing heat exchange between the refrigerant and indoor air to vaporize/condense the refrigerant; and a linear expansion valve 8 for expanding the refrigerant condensed by one of the outdoor and indoor heat exchangers to decompress the condensed refrigerant such that the decompressed refrigerant is introduced into the other of the outdoor and indoor heat exchangers.
On the common inlet pipe of the compressors 1a and 1b is mounted an accumulator 10 for accumulating liquid refrigerant to prevent the liquid refrigerant from being introduced into the compressors 1a and 1b. 
On the outlet pipes of the compressors 1a and 1b are mounted check valves 3a and 3b for preventing back-flow of the refrigerant, respectively.
On the common outlet pipe of the compressors 1a and 1b is mounted a four-way valve 12 for changing flow of the refrigerant according to selected operation mode, i.e., cooling operation mode or heating operation mode.
The opening level value of the linear expansion valve 8 is increased or decreased to control the flow rate of the refrigerant according to cooling load or heating load. The increase and decrease of the opening level value of the linear expansion valve 8 are decided according to comparison between the desired temperature and the current temperature.
The cooling cycle apparatus further comprises: a microcomputer 20 for controlling the four-way valve 12 according to the cooling operation mode or heating operation mode, and controlling the compressors 1a and 1b and the linear expansion valve 8 according to the cooling load or the heating load.
In the conventional cooling cycle apparatus and the method of controlling the linear expansion valve of the conventional cooling cycle apparatus, however, the linear expansion valve 8 is controlled according to comparison between the desired temperature and the current temperature. Consequently, when the length of the pipes is increased or the amount of refrigerant is not sufficient, the cooling cycle apparatus does not quickly deal with load. Furthermore, discharge temperature of the compressors 1a and 1b is increased, and therefore, the compressors 1a and 1b are damaged.